A 28 year-old HIV-positive man came to the doctor’s office complaining of an oral...

A 28 year-old HIV-positive man came to the doctor’s office complaining of an oral infection. The tongue and oral cavity were coated with a whitish, patchy infection. Samples of the substance revealed oval yeast cells connected to one another long filaments.

This sounds like thrush. Thrush (more properly referred to as oral candidiasis) is a fungal infection caused by the yeast-like fungus Candida abicans. When the infection is present in mucous membranes in the mouth (most often on the tongue), it can be referred to as thrush.

Candida albicans is actually a very common fungus and is present in the internal microbial flora of about half of all people. For the majority of people, this fungus poses no real health threat. But for people with weakened immune systems (like newborn children, the elderly, or people with HIV), C. albicans can become infectious and cause thrush. The standard unicellular form of the fungus can change into an infectious multicellular form connected via filaments through a process called dimorphism.

C. albicans is present in most humans as part of the "gut flora." This means that it is one of the numerous strains of bacteria that inhabit the mouth and gastrointestinal tract. Thrush can also manifest itself in the vagina in women.